[clang] [llvm] [llvm][AMDGPU] Fold `llvm.amdgcn.wavefrontsize` early (PR #114481)

[Joseph Huber via llvm-commits]

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@@ -1024,6 +1024,15 @@ GCNTTIImpl::instCombineIntrinsic(InstCombiner &IC, IntrinsicInst &II) const {
     }
     break;
   }
+  case Intrinsic::amdgcn_wavefrontsize: {
+    // TODO: this is a workaround for the pseudo-generic target one gets with no
+    // specified mcpu, which spoofs its wave size to 64; it should be removed.
+    if ((ST->getCPU().empty() || ST->getCPU() == "generic") &&
+        !ST->getFeatureString().contains("+wavefrontsize"))
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jhuber6 wrote:

Unsure if we even need to bother checking for 'generic' since that's not what any of the existing targets use for generic AFAIC. It's just not setting `-mcpu` when you compile, which I think should probably be an error in the backend.

https://github.com/llvm/llvm-project/pull/114481